The world's largest museum complex, the Smithsonian has 16 phenomenal museums and galleries, plus a zoo. Some highlights include the National Air and Space Museum which has full-size air and spacecraft, including the Wright brothers' plane and the command module of the 1969 Apollo 9 mission, and the National Museum of Natural History which houses a fantastic mish-mash of a collection which includes the Hope Diamond, dinosaur bones, insects, a hall of gems and minerals. Or check out the National Museum of American History, home to the original American flag, the original Kermit the Frog, Fonzie's leather jacket, and Dorothy's ruby slippers. Admission to the Smithsonian Museums is free.